The present invention relates to a switch mechanism for indicating a four-wheel drive mode of operation of an automobile transfer gear unit which is selectively actuatable in a two-wheel or four-wheel drive mode in one of high-speed, neutral, and low-speed gear positions.
There has been known a switch mechanism for energizing an indicator lamp when an automobile is in a four-wheel drive mode. The known switch mechanism is actuatable by a changeover fork shaft shiftable in a transfer gear unit to select a two-wheel drive mode or a four-wheel drive mode, there being also a second changeover fork shaft for selecting either a high-speed, neutral, or low-speed gear train. With the prior switch mechanism, the indicator lamp remains energized as long as the changeover fork shaft is in a four-wheel drive position irrespectively of whether the high-speed, neutral, or low-speed gear train is selected by the second changeover fork shaft. Therefore, the conventional switch mechanism is disadvantageous in that, while in the four-wheel drive mode, the indicator lamp is lighted even when the gear is in the neutral position and thus no engine power is transmitted to the four wheels.
One solution to this problem is to add a second switch mechanism actuatable in response to operation of the second changeover fork shaft for energizing the indicator lamp only when the second changeover fork shaft is in the high-speed or low-speed gear position while the four-wheel drive mode is selected by the first changeover fork shaft. This arrangement, however, requires two switch mechanisms, and necessitates an electric control circuit for processing signals from the two switch mechanisms.